1. Field of the Invention
This invention relates generally to the field of polishing infrared detector surfaces and specifically to electro-etching the surface of a mercury-cadmium-telluride ((Hg,Cd)Te) substrate.
2. Prior Art
In the past, polishing the surface of a semiconductor substrate to achieve a smooth surface has been accomplished by pure chemical etching. This was sufficient for relatively coarse smoothing but was inadequate for fine smoothing as required for an infrared detector of (Hg,Cd)Te. In the present case, the density of detectors and the intrinsic nature of the detector itself demands a degree of polishing unknown before. In particular, the semiconductor substrate surface of infra-red detectors in space satellite applications require a degree of polishing smoothness that cannot be achieved by mere chemical etching in order to achieve the desired sensitivity.
It has been known that electro-etching had the potential for fine smoothing/polishing etching, but till now was very difficult to control due to the propensity of the etching process to incur unwanted oxide growth on the object being etched. Accordingly, there was a need for a controlled process using electro-etching that could be combined with chemical etching for fine and coarse etching respectfully to achieve a greatly enhanced polished surface of a (Hg,Cd)Te infrared detector.